Generally, a hybrid vehicle refers to a vehicle in which a motor of an electric vehicle is applied to a conventional internal combustion engine, or a combination of two or more driving sources such as a combination of an internal combustion engine and a fuel cell is applied. Therefore, the hybrid vehicle is an eco-friendly vehicle and has many improved parts in fuel efficiency and performance compared to conventional vehicles.
The hybrid vehicles have been designed by various methods by different manufacturing companies. For example, a transmission mounted electric device (TMED) method in which an electric motor is installed on an automatic transmission may be used, and the hybrid vehicle to which the TMED method is applied has a structure in which an engine clutch is installed between the engine and the (electric) motor to connect or release the engine and the motor.
Recently, as environmental problems have become an issue in the vehicle industry, methods for efficiently processing exhaust gas from the vehicle have been focused. Particularly in the hybrid vehicle, a catalyst may be used to reduce the exhaust gas of the engine during cold start. However, since an activation temperature of the catalyst is significantly greater than room temperature, the catalyst temperature may be elevated by driving the engine and thus the catalyst may be activated.
In the related arts, to solve the above problem, an ignition angle may be sufficiently retarded to decrease kinetic energy and increase heat energy from the energy generated in the engine. However, in this process, vibration may be generated in the engine when the ignition angle is excessively retarded. Moreover, when the engine torque is required, the ignition angle may be retarded sufficiently. Particularly, since the conventional system has a structure in which the engine and a power output shaft are physically coupled with each other and the vibration of the engine may be easily transferred to a driver and output demand torque of the driver together with the engine, the ignition angle may be limited in use for the conventional system. As such, shortening a time for activating the catalyst may not be obtained by increasing the exhaust temperature in the initial stage.
In the related arts, a method of activating the catalyst in the hybrid vehicle has been provided by increasing the catalyst temperature in addition to controlling the retardation of the ignition angle of the engine. For example, a motor of the hybrid vehicle controls a negative (−) torque to be generated and the engine generates additional torque that corresponds to the negative (−) torque of the motor, and thus, heat may be generated by the engine and the catalyst may be activated by the heat. However, as the additional torque is generated in the engine, vibration, noise, and the like may be undesirably generated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that is not considered as a prior art that is already known in this country to a person of ordinary skill in the art.